Conventionally used is a battery sensor for detecting the state of a battery in the field of vehicles or the like. The battery sensor of this type is disclosed in, for example, Patent Documents 1 to 4.
The conventional battery sensor will be briefly described with reference to FIGS. 8 and 9. As shown in FIGS. 8 and 9, the conventional battery sensor 1 includes a battery post terminal 4, a harness connecting part 6 and a casing 8.
The battery post terminal 4 is mounted to a battery post 3 included in a battery 2. The battery post terminal 4 is made of a metal plate formed by a stamping or bending process. As shown in FIGS. 8 and 9, the battery post terminal 4 has a battery post connecting part 20 being in a substantially cylindrical shape. When the battery sensor 1 is mounted to the battery 2, a tightening bolt 21 is tightened under a state where a battery post connecting part 20 receives the battery post 3 therein, so that the battery post connecting part 20 bites into a peripheral surface of the battery post 3. As a result, the battery sensor 1 is (electrically and mechanically) connected to the battery post 3.
A harness connecting part 6 is connected to a harness 5 that is connected to a load (not shown). The harness connecting part 6 has a bolt (stud bolt) 17. On the other hand, the harness 5 has, in its end portion, a terminal 13 (FIG. 8). As shown in FIG. 8, the bolt 17 of the harness connecting part 6 is received through the terminal 13, and additionally a nut 18 is tightened to the bolt 17. This structure, which enables the harness 5 to be (electrically and mechanically) connected to the harness connecting part 6.
The casing 8, having a box-like shape, is generally made of a synthetic resin. The circuit board (not shown) having an electric circuit for detecting a state of the battery 2 is provided in the casing 8. The casing 8 has a connector 14 that outputs a result of the detection by the electric circuit. Though not shown in the drawings, a cable that outputs the result of the detection is connected to the connector 14.
As shown in FIG. 9, a vent plug (cap) 7 for replenishing battery liquid is arranged on the upper surface of the conventional battery 2. Therefore, the battery sensor 1 needs to be arranged so as not to overlap on the vent plug 7. If the battery sensor 1 is arranged so as to overlap on the vent plug 7, the vent plug 7 cannot be opened and thereby the battery liquid cannot be replenished.
FIG. 1 of Patent Document 4 shows a situation where a battery sensor is arranged so as not to overlap on a vent plug of the battery liquid.